The Political Approach to the Classical World 21 The introduction of writing in the Near East seems to have coincided more or less with the introduction of the technique of metal-working on a large scale. Before this, that is to say in that stage of man's development sometimes called the 'Chalcolithic' period, when copper was still a rare and precious commodity, and the working of stone was therefore a laborious and costly process, fine pottery was the chief output of the artistic work- shops. And so the age before bronze is marked almost univer- sally by the fine painted pottery which it produced. In Persia, in Mesopotamia, in Syria, in Egypt such pottery is found, differ- ing widely in its shapes, its designs, and its technique, but having in common that careful workmanship which makes it the finest artistic product of its time. How long this prehistoric age lasted we do not know. The Persian Gulf, gradually receding, left in its wake marshes and salty lagoons. As these dried up, patches of dry land appeared; the Tigris and the Euphrates brought down fertile mud and deposited it at their mouths, and the land of Sumer rose from the sea. Into this now habitable land came down people from the Iranian highlands, who settled in the valley, building their villages of 'wattle and daub' on reed plat- forms in the marshy ground, tilling the patches of dry land and moving about the lagoons in reed boats, just as the Marsh Arabs of Southern Iraq do to this day. To the north and west another group of peoples occupied Subartu in the apex of the Fertile Crescent, an area stretching from Syria on the west by way of the valleys of the Euphrates and Khabur rivers to the upper waters of the Tigris. These, the owners of the most handsome pottery of the age, followed a mode of life very different from that of the marsh dwellers of Sumer. Their houses were already of brick and stone, their villages walled, with cobbled streets. The pre-dynastic peoples of Egypt needed less protection from the weather; their rude huts were often mere wind-shelters. In the reeds of the Nile swamps they hunted the hippopotamus, and on the edge of the valley they cultivated grain and flax.